Yes, you can! It's not quite like MtG, in that you cannot play a card when it's not your turn. You play counter spell on your turn, which deploys a hidden enchantment that will trigger on the next enemy spell cast. If you have a counter spell already setup, it will counter the enemy counter spell as it's being cast. There's an interesting design consideration here: should your counter spell trigger on the opponent's turn as they are casting their counter spell card (which would be a surprise normally) or should it counter their counter spell when it triggers?

I'd rather go for version A, for two reasons:First the counter spell doesn't carry over too long, which might become hard to follow for the players.Second the logic in example B, while rationale, is hard to explain, maybe even accept. In contrast in example A it is very straightforward.

This brings a question to my mind: whenever such a spell is cast (counter spell, trap, etc.), what will the opponent see? Nothing? The summoner casting something without any further detail? The summoner casting something and how much mana he spent, without knowing to what purpose?

This brings a question to my mind: whenever such a spell is cast (counter spell, trap, etc.), what will the opponent see? Nothing? The summoner casting something without any further detail? The summoner casting something and how much mana he spent, without knowing to what purpose?

I'm glad you asked, this, Scribe. I haven't made this decision yet, and it's a vital part of the counter spell sequence. In Hearthstone, when a surprise/interrupt/secret card is played by your opponent, you will see a card popup that reads "Secret: This is hidden until a secret action occurs... Watch out!" and the cost of the card will also be revealed.

So, at the time the secret is played, you are aware there is a secret on the board and how much it costs. If we were going by Hearthstone logic, Example A, would be the appropriate flow.

I think there are pro's and con's to Hearthstone's implementation. At its core, the mechanic aims to represent the feel of an "instant/interrupt" spell as it would be played in a game like Magic the Gathering (where it is possible to cast the counter spell during your opponent's turn) - but it seeks to eliminate the complicated synchronization problem of actually playing the card on your opponent's turn (which I do agree is the better course of action for game pacing online). The doubt I have is: "Do you really feel surprised if you are told upfront that a surprise card has been placed on the board?" The surprise effect is further diminished when you can see the cost of the card and (if you're familiar enough with the cards) can probably guess what the actual surprise card is.

I've been considering a more subtle approach that I hope might create a more effective "Surprise!" moment and I would love to get your feedback. My idea is: As the opponent of someone who is playing a surprise card, you would see nothing - not the cards in player's hand nor the mana available to that player. Game tropes have made these two pieces of information as "obvious and taken for granted that they should be known" but I challenge that for a digital game where the ability to hide this information easily exists, you can control cheating, and you can then make up for other mechanics (playing cards on opponents turn) that are harder to do well in the digital space.

From a gameplay perspective, the "subtle clue" for a surprise card being played comes from the observation that an opponent did not cast a spell on their turn. This leaves you to wonder: Is my opponent saving up mana for a 5 drop next turn? Or, did they spend their mana to cast a surprise card? There's a lot more tension there and a lot more surprise elements to consider. Since I've removed a lot of the randomness by eliminating dice rolls, I was thinking this might help bring back some of the excitement you feel when something unexpected happens.

I think it's certainly worth trying. I agree that the surprise should then probably be total, which should be good for keeping the game entertaining. As long as the player understands what happened. Do you plan on showing the "secret" card once triggered?

Yes, with the "total surprise" (Option B), you would first see something like "Surprise!" to indicate a surprise event has triggered, followed by an animation of the opponent Summoner performing a cast and revealing the Counterspell card. For a trap, you'd see the "Surprise!" followed by the trap card being shown, then the damage/effect animation would play out.